Direct bonding of Germanium and Diamond substrates by reduction process

For efficient heat dissipation from Ge-based high-speed devices, we performed direct bonding of Ge and diamond substrates. The conventional hydrophilic bonding process employs oxidizing pre-bonding treatment; however, this process develops a thick oxide layer at the bonding interface. In this study, the Ge substrate was reduced by HCl acid and then bonded with the diamond substrate. The thickness of the bonding interface was 1.6 µm, which is significantly thin compared with the previous studies using the oxidizing treatment.